Bone marrow stromal stem cells (BMSSCs) have a limited in vitro differentiation potential and are observed to senescence and die after no more than 30-40 population doublings (PD). But, two papers in June Nature Biotechnology, show that overexpression of telomerase in human bone marrow stromal cells extends their life span and maintains their osteogenic potential.

Songtao Shi and colleagues at US National Institutes of Health (NIH), Bethesda, observed that BMSSCs transduced with human telomerase reverse transcriptase (hTERT) lived longer than controls. In addition hTERT-expressing BMSSCs generated more bone tissue, with a mineralized lamellar bone structure and associated marrow. The bone-forming ability correlated with sustained expression of the early pre-osteogenic stem cell marker STRO-1. This inicates that "telomerase expression helped to maintain the osteogenic stem cell pool during ex vivo expansion," conclude the authors.

In the second paper, Janne Simonsen and colleagues at University Hospital of Aarhus, Denmark...

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